Java Write Files

Write To a File

If you are just starting with Java, the easiest way to write text to a file is by using the FileWriter class.

In the example below, we use FileWriter together with its write() method to create and write some text into a file.

Note: When you are done, you should close the writer with the close() method:

Example

import java.io.FileWriter;   // Import the FileWriter class
import java.io.IOException;  // Import the IOException class

public class WriteToFile {
  public static void main(String[] args) {
    try {
      FileWriter myWriter = new FileWriter("filename.txt");
      myWriter.write("Files in Java might be tricky, but it is fun enough!");
      myWriter.close();  // must close manually
      System.out.println("Successfully wrote to the file.");
    } catch (IOException e) {
      System.out.println("An error occurred.");
      e.printStackTrace();
    }
  }
}

Explanation: This program tries to write some text into a file named filename.txt. If everything works, the program will print "Successfully wrote to the file." in the console. If something goes wrong (for example, the file cannot be opened), it will print "An error occurred." instead.

Write To a File with try-with-resources

Since Java 7, you can use try-with-resources. This makes sure the writer is closed automatically, even if an error occurs:

Example

import java.io.FileWriter;
import java.io.IOException;

public class WriteToFile {
  public static void main(String[] args) {
    // FileWriter will be closed automatically here
    try (FileWriter myWriter = new FileWriter("filename.txt")) {
      myWriter.write("Files in Java might be tricky, but it is fun enough!");
      System.out.println("Successfully wrote to the file.");
    } catch (IOException e) {
      System.out.println("An error occurred.");
      e.printStackTrace();
    }
  }
}

Append to a File

Normally, FileWriter will overwrite a file if it already exists. If you want to add new content at the end of the file (without deleting what's already there), you can use the two-argument constructor and pass true as the second parameter. This puts the writer into append mode:

Example

import java.io.FileWriter;
import java.io.IOException;

public class AppendToFile {
  public static void main(String[] args) {
    // true = append mode
    try (FileWriter myWriter = new FileWriter("filename.txt", true)) {
      myWriter.write("\nAppended text!");
      System.out.println("Successfully appended to the file.");
    } catch (IOException e) {
      System.out.println("An error occurred.");
      e.printStackTrace();
    }
  }
}

Explanation: This program adds the text "Appended text!" to the end of filename.txt instead of replacing the file's content.

Note: If the file does not already exist, Java will create it before appending.

Tip: To see what's inside the file, go to the Java Read Files chapter.

Other Ways to Write to Files

There are several classes you can use to write files in Java:

• FileWriter - easiest choice for basic text.
• BufferedWriter - better for large text files, because it is faster and supports handy features.
• FileOutputStream - best for binary data (images, audio, PDFs)

You will learn more about FileOutputStream and BufferedWriter in a later chapter.